1. Technical Field
The present invention relates to electric rotating machines that are used in, for example, motor vehicles as electric motors and electric generators.
2. Description of the Related Art
There are known electric rotating machines which include a rotor and a stator. The rotor has a plurality of pairs of magnetic poles that are arranged in a circumferential direction of the rotor. The stator includes a stator core and a stator coil. The stator core has a plurality of slots, which are arranged in a circumferential direction of the stator core, and is radially opposed to the rotor. The stator coil is comprised of a plurality of phase windings each of which is wound on the stator core so as to be inserted in corresponding ones of the slots of the stator core.
Moreover, to secure high output of the electric rotating machine, the stator core is configured to have, for each of the phase windings of the stator coil, a plurality of circumferentially-consecutive single-phase slots, in which only the phase winding is received, per magnetic pole of the rotor.
For example, Japanese Patent Application Publication No. 2000-69729 (to be simply referred to as Patent Document 1 hereinafter) discloses a three-phase stator coil that is wave-wound on a stator core that has two single-phase slots per phase winding of the stator coil and per magnetic pole of the rotor.
More specifically, as shown in FIG. 26A, the stator coil is comprised of a U-phase winding, a V-phase winding and a W-phase winding. Each of the U-phase, V-phase and W-phase windings includes a first section (a), a second section (b), a third section (c) and a fourth section (d). The four sections (a)-(d) are sequentially arranged from a terminal of the phase winding at one end of the phase winding to a neutral point of the stator coil at the other end of the phase winding. Further, taking only the U-phase winding as an example, as shown in FIG. 26B, the first section (a) and the fourth section (d) of the U-phase winding are received in the same single-phase slots U1 of the stator core, while the second section (b) and the third section (c) of the U-phase winding are received in the same single-phase slots U2 of the stator core. That is, the first and fourth sections (a) and (d) are received in different ones of the single-phase slots for the U-phase winding from the second and third sections (b) and (c). Here, the single-phase slots U1 are circumferentially spaced from one another by one magnetic pole pitch (i.e., a pitch between the N and S magnetic poles of the rotor); the single-phase slots U2 are also circumferentially spaced from one another by one magnetic pole pitch; each of the single-phase slots U1 is positioned immediately adjacent to one of the single-phase slots U2. In addition, it should be noted that the V-phase and W-phase windings of the stator coil are wound on the stator core in the same manner as the U-phase winding.
Japanese Patent Application Publication No. 2004-64914 (to be simply referred to as Patent Document 2 hereinafter) discloses a three-phase stator coil that is wound on a stator core in a manner that is a hybrid of a lap winding manner and a wave winding manner. The stator core has three single-phase slots per phase winding of the stator coil and per magnetic pole of the rotor. Further, in each slot of the stator core, the stator coil is received in six layers in a radial direction of the stator core. More specifically, the stator coil is first lap-wound around the stator core so as to fill the radially-inside four layers in each slot of the stator core and then wave-wound around the stator core so as to fill the radially-outside two layers in each slot of the stator core. Furthermore, each phase winding of the stator coil includes first to sixth sections. For each phase winding of the stator coil, the first section and the sixth section (i.e., the last section) of the phase winding are received in the same single-phase slots for the phase winding.
That is, in both Patent Document 1 and Patent Document 2, for each phase winding of the stator coil, the first and the last sections of the phase winding are received in the same single-phase slots for the phase winding.